Wheatstone bridge & strain gauges worksheet with answers

Free printable Wheatstone bridge & strain gauges worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 80 Ω, R₂ = 80 Ω and R₃ = 500 Ω. Find the unknown resistor R₄.

R₁ = 80 ΩR₂ = 80 ΩR₃ = 500 Ω

R₄ = Ω

2.Easy

The bridge shown is supplied with V_s = 5 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 5 VR₁ = 60 ΩR₂ = 40 ΩR₃ = 60 ΩR₄ = 1000 Ω

I_s = mA

3.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 500 Ω

P_g = mW

4.Medium

A bridge has four 200 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 1 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 9 VR = 200 ΩΔR = 1 Ω

V_ab = mV

5.Hard

A quarter bridge with one active gauge (GF = 2.05) is excited with 10 V. Under load the output reads 1.281 mV. Find the strain ε in µε.

V_s = 10 VGF = 2.05V_o = 1.281 mV

ε = µε

6.Hard

A strain gauge (GF = 2.05) on a member with E = 200 GPa forms a quarter bridge excited with 3 V. The output reads 1.23 mV. Find the axial stress σ in MPa.

V_s = 3 VGF = 2.05V_o = 1.23 mVE = 200 GPa

σ = MPa

Answer key

1. R₄ = 500 Ω
2. I_s = 54.72 mA
3. P_g = 12.5 mW
4. V_ab = 11.25 mV
5. ε = 250 µε
6. σ = 160 MPa

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